“Broad loom tufting machines” typically use a row of several hundred needles to insert row after row of tufts simultaneously into backing fabric which is drawn continuously passed them. Such large scale machines commonly use needles which have an eye to carry the yarn through the backing. It is common practice in broadloom tufting machines to switch between cut pile and loop pile on a stitch by stitch basis, or area by area basis, automatically, and under the control of bit map design data from a design system. Cutting of the yarn is generally done after tuft insertion by means located on the opposite side of the backing fabric to the needles.
U.S. Pat. No. 3,389,667 (H. C. Mueller) describes an early hand-held tufting gun. This gun uses a single hollow needle, and incorporates a cutting mechanism that cooperates with the needle's reciprocating action to produce cut pile. The cutting mechanism is manually engaged and disengaged to switch between cut and loop pile. The patent also describes a ganged arrangement where the cutting mechanism associated with each needle is controlled by a respective pattern chain which determines whether the cutting mechanism is activated or not in any given tufting cycle. The Hartleb (see DE 2,815,801) and Scholz (see U.S. Pat. No. 3,968,758) hand-held tufting guns are further examples of earlier types of hand guns to which a linear action cutter and a rotary action cutter can be manually engaged and disengaged.
Modern hand-held tufting guns use a hollow needle and a mechanism to cut the yarn after it is inserted in the backing fabric. To switch between cut and loop pile the cutting mechanism must be manually engaged and disengaged, which is tedious and time consuming. At least one manufacturer recommends that two machines be used sequentially, one for cut pile and the other for loop pile.
As a result the carpets and rugs produced by hollow needle tufting guns, whether by hand or by automatic machines, have tended to be constructed entirely of cut pile, or entirely of loop pile. When a mixture of cut pile and loop pile is desired, it is typical to restrict the switching between cut and loop to relatively large and well defined areas of color. It is problematic to have designs in which small runs of cut pile are interspersed with small areas of loop pile. But, there is a growing demand for new textured effects in tufted carpet, including designs which intermingle cut pile and loop pile effects frequently.
A fully mechanical type of hand held tufting gun uses a forked blade, rather than air, to push the yarn through the hollow needle. Machines of this type are able to use a yarn brake so that the forked blade can be used to cut the yarn and produce cut pile. Where loop pile is to be produced the blade is required only to push the yarn into place and not to cut it, and the yarn brake is dispensed with or immobilized. This adjustment can be simple relative to the adjustments required to convert the operation of the pneumatic machines, and a solenoid operated yarn brake can be used to automate the change over. However, it is recommended to change the sharp forked blade for a blunt one when producing loop pile, so that inadvertent damage to the yarn is avoided. Naturally, the sharp blade must be restored when switching back to cut pile.
Furthermore, the forked blade type of machine is unable to offer some of the stitching capabilities of the pneumatic machines, such as the ability to reliably tuft and cut some types of non-woolen yarns, especially when multiple ends of different thickness yarns are tufted simultaneously. The production of exaggerated “J” shaped cut pile tufts is not possible, since both legs of the tuft produced are essentially the same length, making a “U” shaped tuft.
The hollow needle used for this type of tufting has a sharp point created by cutting the cylindrical needle at an angle of 45 degrees. In operation the needle must be oriented such that the tip faces the direction of tufting. When the direction of tufting changes, so must the needle. This is accomplished with manually controlled handguns typically by rotating the entire tufting gun about a hand held swivel, in a range of approximately 180 degrees. This is problematic for automatic operation for several reasons: The yarn feed, electrical supply wires, and pneumatic supply hoses required for operation prevent the head from being rotated continuously through multiple turns. The mass of the parts that must be rotated restrict the rotational speed which reduces the overall speed with which automated tufting machine can be driven, reducing productivity of the machine. Various techniques have been used in the past for rotating the entire or a portion of the tufting mechanism, for example as described in Wilcom Tufting's earlier patent U.S. Pat. No. 5,829,372 which uses a mechanical “needle and blade” tufting mechanism. These are not adaptable for use in pneumatic tufting guns such as the Hartleb type gun described in DE 2,815,801.
Wilcom Tufting Pty Ltd has another earlier U.S. Pat. No. 5,503,092 and this together with U.S. Pat. No. 5,829,372 give details of the tufting and cutting cycles of operation.
None of the mechanisms proposed or used for automatically changing between cut and loop pile in broad loom or ganged arrangements of tufting machines have proved to be adaptable to single needle tufting guns, whether guided manually by a human operator, or automatically via a computer controlled machine using vector based design definition.